This invention relates to a circuit breaker and more particularly to an improved latchable operating mechanism in which the changa lever includes a springclip member attached thereto to dampen vibrations which are created in the circuit breaker that cause undesired arbitrary opening of the circuit breaker.
Circuit breakers provide protection for electrical systems from electrical fault conditions such as current overloads and short circuits. Typically, circuit breakers include a spring powered operating mechanism which opens electrical contacts to interrupt the current through the conductors on an electrical system in response to abnormal currents. The operating mechanism is unlatched by a trip bar which in turn is operated by a trip mechanism associated with each phase of the electrical system. The trip mechanism can include a magnetic trip device comprising a fixed magnetic structure energized by the current flowing through the conductor, and a movable armature which is attracted toward the stationary magnetic structure to operate the trip bar. The trip bar in turn unlatches the operating mechanism to open the electrical contacts in each phase of the electrical system. The movable armature is biased away from the stationary magnetic structure by a spring thereby forming a gap between the armature and the stationary magnetic structure in the absence of an abnormal current.
In one type of circuit breaker, the trip bar includes a projection which when the circuit breaker is in a closed position engages against a portion of a changa lever. This portion is biased against the trip bar projection so that when the trip bar is rotated, this portion moves. This movement ultimately causes the latch lever of the latchable operating mechanism to become unlatched from the cradle of the over center toggle mechanism which in turn opens the electrical contacts to interrupt the circuit. The projection and the portion of the changa lever have surface-to-surface contact at a small (approximately 1/32 inch) contact area. Because of this, vibrations in the circuit breaker, caused, for example, when the circuit breaker is reset from an open to a closed position, can cause undesired disengagement of the projection from the changa lever thus leading to arbitrary opening of the circuit breaker.
What is needed, therefore, is a means to dampen vibrations in the changa lever to resist undesired disengagement of the changa lever from the trip bar projection, while at the same time maintaining acceptable performance of the changa lever.